The bow and arrow is a projectile weapon system that predates written history. The bow is a flexible arc which shoots aerodynamic projectiles called arrows. Generally, the two ends of the bow are joined together with a string such that when the string is drawn back, the ends of the bow are flexed. An arrow is placed upon the string and the string is drawn back. When the string is released, the potential energy of the flexed stick is transformed into the velocity of the arrow. Bows and arrows have historically been important weapons, but are used primarily for hunting and the sport of archery today.
An arrow generally consists of a shaft with an arrowhead attached to the front end, with fletchings and a nock at the other. Modern arrows may be made of any suitable material, including but not limited to carbon fiber, aluminum, fiberglass, and wood shafts. Carbon shafts have the advantage that they do not bend or warp, but they can often be too light weight to shoot from some bows and are expensive. Aluminum shafts are less expensive than carbon shafts, but they can bend and warp from use. Wood shafts are the least expensive option but often will not be identical in weight and size to each other and break more often than the other types of shafts.
The end of the arrow that impacts the target is the arrowhead. Historically, arrowheads have been made from various materials including flint, bone, horn, or metal. Most modern arrowheads are made of steel, but wood and other traditional materials are still used occasionally. Typically, the arrowhead is provided or manufactured separately from the arrow shaft and is attached to the arrow. For example, the arrowhead can be attached by tangs or sockets. Among arrowheads, three common types include bodkins, broadheads, and piles. Bodkin heads are simple spikes made of metal of various shapes. A broadhead arrowhead is usually triangular or leaf-shaped and has a sharpened edge or edges. Broadheads are commonly used for hunting. A pile arrowhead is a simple metal cone, either sharpened to a point or somewhat blunt, that is used mainly for target shooting.
As noted above, a broadhead is a particular type of arrow head which has outwardly extending blades that are designed to inflict more extensive damage to the animal. An objective for any broadhead is to have the animal killed as quickly as possible such that the animal will not suffer for a long period of time and so that the animal will be recoverable by the hunter. Typically, modern hunting arrows comprise a fiberglass or graphite shaft on which the broadhead body is threadably mounted.
There is a need for an improved broadhead. The flight of prior art broadheads in which the blades are secured on the orrow in a fully open position was adversely affected by wind resistance acting against the exposed broadhead blades. Accordingly, broadheads with fixed blades tend to be less accurate because of wind current deflection and tend to have less velocity because of increased drag. Modern design efforts for broadheads have focused on decreasing the wind effects to ensure a more accurate and effective broadhead. These efforts typically involve reducing the surface area of a broadhead blade to reduce the undesirable steering effects of the wind. However, by reducing the surface area of a blade, the cutting area within a target or game is also reduced, resulting in a less effective entrance and exit wound.
Conventional blade-opening arrowheads have been designed so that a substantial portion of the blade is hidden within the body of the arrowhead, such as during flight of the arrow. Upon impact, such blades are designed to open and thereby expose a cutting surface or sharp edge of the blade. When the blades of such conventional arrowheads are closed and substantially hidden within the body, the exposed, surface area is reduced and thus produces relatively less undesirable steering effects. Unfortunately, these blade-opening arrowheads are often complex mechanically and include a significant force holding the blades close. This significant force can be difficult to overcome, and these devices may fail to open reliably. Others have structural defects within the body that can result in premature opening of the blade. In either case, the arrow does not penetrate the target. Examples include U.S. Pat. Nos. 5,112,063, 4,998,738 and 5,082,292. In these examples, the deployable cutting blades are connected by pivot features to a plunger. The cutting blades pivot between an open cutting position and a closed non-barbed position. In U.S. Pat. No. 5,102,147, a ballistic broadhead assembly has blades pivotally mounted on an actuating plunger. Upon impact, the actuating plunger thrusts the blades outwardly and forwardly.
Other broadheads which have blades partially hidden within the body use annular retaining rings, such as O-rings, wraps, bands and the like, in order to maintain the blades in a closed position during flight. Upon impact, such annular retaining rings are designed to sheer or roll back along the opening blades, in order to allow the blades to move to an open position. These conventional annular retaining rings are prone to cracking, particularly when the elastomer material dries out. Upon release of a bowstring, the rapid acceleration and thus significant opening forces move the blades in an opening direction. The conventional annular retaining rings counteract the opening forces, but fail of the ring material is brittle or damaged. Moreover, many of the annular retaining rings are designed for one use and thus must be replaced after each use. In addition to the cost involved with supplying such consumable item, the annular retaining rings are difficult and time-consuming to install, such as when hunting, particularly during inclement weather. Furthermore, the material properties of such conventional annular retaining rings can be affected by temperature changes, thereby resulting in different bias forces that cause the blade to open prematurely or to not open when desired.
A final group of mechanical broadheads deploys the blades in an over-the-top motion, such as that disclosed in U.S. Pat. No. 5,090,709. The extendable blades are pivotally connected to a body near the rear of the broadhead body. A ring releasably holds the extendable blades within corresponding slots within the body. These over-the-top broadheads often fail when the blades do not fully open until after the blades enter the target. Consequently, the full cutting diameter of an over-the-top broadhead is often not available through the depth of the target.